Thank you for your answer.
As I guess my customer will not agree seing JBoss specific annotations on its EJB3, I wonder if it may be possible to add annotations at deployment thanks to an "AOP domain" as described here: http://docs.jboss.org/ejb3/docs/reference/1.0.7/html/SessionBean_and_MDB_configuration.html
By the way, I will give a try to JBoss 7 too.